In recent years, the theory that water containing a large amount of hydrogen is effective in removing active oxygen, which causes various kinds of diseases, including cancer, has been published in the medical world and has gathered attention. A hydrogen water generator using the chemical reaction between magnesium particles and water is a known hydrogen water generator that generates water containing plenty of hydrogen. This kind of hydrogen water generator includes a case, configured to be placed in a bottle for drinking water and to be filled with water, and a water-permeable bag, disposed in the case and filled with magnesium particles, which are capable of reacting with drinking water to generate hydrogen gas (for example, see Patent Document 1).